20、He forgot to ________ the lights before he left.
(A) shut down
(B) shut in
(C) shut off
(D) shut away

(A) shut down: 關閉 (guānbì) - This generally means to stop the operation of something, like a machine, a business, or a system.

(B) shut in: 禁閉 (jìnbì) or 把...關在裡面 (bǎ...guān zài lǐmiàn) - This means to confine someone or something in a place, preventing them from leaving.

(C) shut off: 關掉 (guāndiào) - This usually refers to stopping the flow of something, like water, electricity, or gas, by turning a valve or switch.

(D) shut away: 隔離 (gélí) or 藏起來 (cáng qǐlái) - This can mean to isolate someone or something, or to hide something out of sight. The nuance depends on the context.